Question

A pendulum bob of mass 50g is pulled aside to a vertical height of 20cm from the horizontal and then released. Find (i) The maximum potential energy of the bob. (ii) The maximum speed of the bob. (iii) The K.E of the bob when it is at a height of 8 cm from the horizontal.​

Answer 1

PE (bob) = M g H = .05 kg * 9.8 m/s^2 * .2 m = .098J

i) max PE = .098 J

1/2 M V^2 = .098 J maximum speed of pendulum

V^2 = .196 / .05 = 3.92 m^2 / s*2

(ii) V = 1.98 m/s max speed of bob

PE of bob at .08 m = .05 * 9.8 * .08 = .0392 J

(iii) KE of bob at .08 m = (.098 - .0392) J = .0588 J